Beverages based on the tea plant (Camellia sinensis) have been popular throughout the world for many hundreds of years. Traditionally such beverages are produced by infusing leaf tea in hot water.
Most of the tea consumed in the Western World is so-called black tea which is obtained by harvesting leaves of the plant Camellia sinensis and withering, rolling, enzymatically oxidizing (fermenting), firing and sorting them. However the leaves can be processed without the fermentation step to produce what is known as green tea. Such tea is widely consumed in parts of the People's Republic of China, Japan, North Africa and the Middle East. In another variation oolong tea is prepared by partial fermentation.
Tea leaves contain a large number of enzymes, biochemical intermediates and structural elements normally associated with plant growth and photosynthesis together with substances that are responsible for the characteristics of tea itself. These include flavanols, flavanol glycosides, polyphenolic acids, caffeine, amino acids, mono- and polysaccharides, proteins, cellulose, lipids, chlorophylls and volatiles.
Flavanols or more specifically flavan-3-ols tend to constitute up to 30% of the dry weight of freshly picked tea leaves and are known as catechins. Green tea retains most of the catechins, but their content in black tea is greatly reduced due to both chemical and enzymatic oxidations taking place during fermentation to give theaflavins and thearubigins.
Catechins have been claimed to possess a variety of biological activities including anti-tumour activity and effects on modulating body shape and/or body fat.
As well as affecting tea colour, theaflavins have been recognised as providing the “brightness” and “briskness” quality attributes of black tea. In fact, theaflavin content is known to correlate with the quality of black tea. Moreover, theaflavins have been shown to have several positive health benefits. The purported benefits include lowering blood lipid levels (e.g. cholesterol), anti-inflammation effects and anti-tumour effects.
Tea contains many other phenols. These include gallic acid, flavanols such as quercetin, kaemferol, myricetin, and their glycosides; and depsides such as chlorogenic acid and para-coumarylquinic acid. Some of these are believed to participate in the chemical reactions that occur during fermentation.
Green tea contains many more catechins than black tea. However despite the burgeoning health consciousness amongst many consumers green tea is usually dismissed in Western countries as being too pale and unpleasant to taste. Furthermore it is typically slow to infuse and therefore not suitable for the Western desire for convenience for the sake of quality. Further still, some of the health benefits afforded by the theaflavins of black tea may not be provided by the catechins of green tea. In order to overcome some of these drawbacks, efforts have been made to provide tea products having the advantageous properties of both black and green tea.
WO 98/23164 (Unilever) discloses a leaf tea comprising a blend of a first substantially fermented tea and a second substantially unfermented tea, characterised in that the blend contains catechins and phenols in a ratio of between 0.15 to 0.4. This document also teaches that the ratio of gallated to non-gallated catechins is related to bitterness and thus tea clones having a low ratio of gallated to non-gallated catechins are preferred.
WO 2009/059927 discloses that the amount of caffeine in tea juice expressed from dhool decreases with the degree of fermentation. Furthermore fermented tea juice typically has a lower proportion of gallated theaflavins compared with conventional tea extracts and the proportion of gallated theaflavins in the juice also varies with the degree of fermentation before expression. Thus we have recognised that fermented tea juice can be added to unfermented tea material to increase the black tea character thereof whilst not imparting excessive bitterness from gallated theaflavins and/or without bringing large amounts of caffeine.
In addition, we have now found that by combining fermented juice with unfermented dhool before deactivating the enzymes in the unfermented dhool, tea products with exceptional infusion performance can be created.